There are various prior art devices known for controlling reciprocating pumps. Many prior art devices use a mechanical control mechanism to drive the piston of the reciprocating pump, but these mechanisms have been unreliable either because they require a number of failure- and/or wear-prone components or because they can stall or vary in stroke frequency in response to varying operating conditions frequently encountered in practical usage.
The pilot control valve disclosed in U.S. Pat. No. 6,183,217 B1 changes the directional flow of control fluid to a piston coupled to the pilot control valve to drive a reciprocating device. U.S. Pat. No. 6,183,217 B1 attempts to improve reliability by controlling the communication of control fluid to a piston included with a reciprocating device using pneumatic valve control rather than a mechanical control mechanism. U.S. Pat. No. 6,736,046 utilizes a slide valve member shiftable within a valve body between a first or “downstroke” position and a second or “upstroke” position. When in its first position, slide valves allow communication of control fluid supplied to the valve body to the lower surface of the piston. As the slide valves move to their second position, they allow communication of pressurized control fluid to the upper surface of the piston causing the piston to return to its first position. Nevertheless, there remain advantages in providing new reciprocating devices which offer still further improvements.